What I have done…
1) I have used Space Claim for drawing the Geometry. 

2) I have inserted my own co-ordinate system.
3) I have meshed using body size and introduced sphere of influence with some radius and element size. Also refined the mesh.

4) Using Named selection and worksheet I tried to select the meshed elements within the sphere of influence. 
5) Using APDL commands I tried to change the material properties of the meshed elements within the sphere of influence.



The solution which you have replied looks more accurate and easy for changing the material properties within in the sphere and I was much interested in trying that.

I am unable to perform Boolean operations in space claim. Please help me in doing this in random places for random bodies. I am attaching my google drive link where you can see whatever I have done.

Thank you!